There are several inventions related to the dosing of elements. The existing dosing systems have two characteristic elements: on one hand the transporting system for transporting the element to be treated, for example pellets, and on the other hand the control system for controlling the amount of elements. The pellets are at first contained in a hopper or tank. By means of the transporting system they are moved from the hopper to another container where the amount of elements to be used in the molding process is accumulated.
U.S. Pat. No. 6,877,933B2 describes a system for dosing pellets in which the pellets are transported by suction through the generation of vacuum. The pellets are transported towards a hopper where they accumulate. The hopper pours its content when a level sensor determines that it is completely full.
Patent JP 2010149894 proposes a system for dosing pellets having a plate with openings in which the pellets falling by gravity from the hopper are retained. The plate with openings is horizontally displaced under the hopper to favor the introduction of the pellets in the openings. A detection system verifies that the openings contain pellets and the content is finally poured into a second hopper.
Patents CN 1474189 and CN 101148224 disclose dosing systems which use a vibrating element to enable the movement of the pellets. The pellets are contained on a horizontal plate to which the vibration is provided. The pellets circulate randomly on the vibrating plate and at some point of their displacement reach an output opening which leads them to a conveyor belt.
In view of the mentioned background, proposing a system which allows dosing a specific but variable number of elements according to needs is necessary and useful. In the mentioned patents U.S. Pat. No. 6,877,933B2 and JP 2010149894 the number of elements obtained is fixed, because it is determined, in the first case, by the capacity of the hopper, and in the second case, by the number of openings of the plate. Obviously, doses of different amounts could be obtained by exchanging these elements with others of different dimensions or amount of openings but it is more convenient to have variable doses without needing to adapt the machine.
The inventors have verified that causing the movement of the pellets by means of controlled vibrations is a valid option, and that complementing the identification of the pellets by electronic detection means improves the functionality of the dosing apparatus.
In the mentioned patents CN 1474189 and CN 101148224 said vibrating systems work continuously. It would be optimal to control the operation of this device and to only cause the vibration at suitable time and not throughout the entire dosing process.
CN 2734627 discloses a granule counting apparatus which includes all the features of the preamble of claim 1 of the present invention. The detection device of the apparatus of CN 2734627 is depicted in the form of a housing coupled to an end side of a vibratory conveying device, not specifying therein where exactly the granule detection is done, if under the discharging end of the vibratory conveyor or before the granule falls. The type of detection performed is not either indicated in CN 2734627.
CN 201882251 discloses a device for counting and weighing granular objects comprising a detection grating for counting the particles falling from a discharging opening of a vibrating tray. The counting which can be performed with such a detection grating, which has to detect simultaneously a plurality of falling granular objects at once, is not as accurate and simple as it would be with other kind of detection device arrangements acting more locally to detect less, preferably one, granular objects at once.
EP 1332793 A1 discloses a process for dosing and mixing particles, e.g. granules, comprising a transport unit moving some particles to an optical unit where they are counted. Said optical unit has an optical detector arranged to count the particles while being transported by the transport unit, which results in a non-accurate detection of the particles as when some of them are too close to each other, a group of such close particles can be detected as if there was only one particle crossing in front the optical detector. Other drawbacks due to said arrangement and location of the optical detector can exist which can generate false or erroneous detections, such as those due to particle clogging or due to the vibrations of the transport unit.